1. Field of the Invention
The present invention relates to an oil field apparatus or tool, and more particularly relates to an improved power wrench brake or drag assembly. Even more particularly, the present invention relates to an improved power wrench brake assembly providing an adjustable brake assembly having external, easily accessible brake drum surface and brake shoe portions which can be quickly field adjusted or field removed/replaced.
2. General Background and Prior Art
In the oil field and in oil/gas drilling, there is often utilized a "power wrench" or "power tong" for making up and braking up sections of drill pipe, casing, or other like piping assemblies which are generally made up into strings from a plurality of joints. Many of these power tongs or power wrenches are in use which quickly make or brake the desired connection using power supplied by an electric or hydraulic motor for example. Generally, power wrenches of this type have a clutch or drag or brake assembly which transforms rotary power through a gear reduction system into gripping power through a cam mechanism, thus allowing the pipe to be gripped at the joint and the desired torque applied. Power wrenches and power tongs of this type are known.
The clutch or drag assembly of a power wrench requires adjustment. This is because the frictional contact between a drum surface and a shoe surface to one or both. Further, adjustment of the drag assembly makes a great deal or torque or a lesser amount of torque (as desired) transferable directly to the gripping jaws of the power wrench. In other words, whether or not the frictional engagement of the drag assembly is great or small determines at least to some extent the force with which the pipe joint will be gripped. The adjustment must be maintained over a long period of time during the drilling operation. As wear occurs on the shoe and/or drum, adjustments must be made to assure the same gripping strength to the pipe. Generally the brake mechanism is internal to the wrench and cannot be adjusted in the field. Adjustment with internal brake assemblies must be performed by a shop mechanic or other technical person who inspects the wrench and readies it for operation at a shop or other site, usually removed from the actual drilling location. Often a portion of the wrench itself must be disassembled to gain access to the brake assembly for replacement/adjustment.
Other prior art type clutch assemblies recommend and teach that a duplicate clutch assembly or drag assembly or brake assembly be kept in the field with the tool to replace the original assembly since field adjustment is impossible or at least very difficult. With such assembly, the shoe and drum are a single unit, with adjustment on the entire unit being possible but when outside the wrench.
When a driller is required to spend excessive down time on the adjustment of a particular part of his drilling equipment, very expensive down time results which loses production for the driller desirous of completing a drilling of the well. Needless to say, time is money and the driller as well as all other persons connected with the drilling of the well desire that it be completed as soon as possible with as little down time to the equipment as possible.
Several devices have been patented which address the concept of a brake or drag apparatus for a power tong. U.S. Pat. No. 2,618,468 issued to C. A. Lundeen and entitled "Power Tong", shows a brake rim and a cooperating stationary brake band.
In U.S. Pat. No. 4,015,661 entitled "Apparatus for Coupling and Uncoupling Pipe Sections", there is shown a pair of brake members which function as a brake apparatus for a power tong.
In U.S. Pat. No. 2,650,070 issued to C. A. Lundeen, there is also seen a friction band having a lining which encircles an upright rim.
U.S. Pat. No. 3,141,362 issued to Simon Tammy and Zenis Weisel provides a "Jaw Operating Structure for a Power Operated Wrench". A annular brake pad 61 is provided with a cooperating drum structure.
U.S. Pat. No. 3,516,308 issued to J. E. Ham and Merrill Willsey provides a power tong transmission assembly which shows a brake band engaged with an annular wall. Further provided with the Ham-Willsey device is a means for applying more or less braking force to the band designated as a brake actuator mechanism.
U.S. Pat. No. 3,540,326 issued to J. L. Dickman provides a "Pipe Tong Head". This patent is also discussed in U.S. Pat. No. 3,516,308.
U.S. Pat. No. 3,589,742 issued to Howard S. Flick and entitled "Jaw Actuating Means for Pipe Tongs" provides a brake band having an inner lining which cooperates with a drum structure.
U.S. Pat. No. 3,625,095 issued to James Barnett provides a brake means for use with power tongs.
U.S. Pat. No. 3,380,323 issued to A. B. Campbell and entitled "Power Wrench" illustrates a braking structure which is comprised of flat annular disc like braking elements. The Campbell device also utilizes as a preferred means for braking a drum and brake shoe structure.
These and other prior art type brake devices for use with power wrenches and power tongs are generally hard to regulate, and are hard to replace. Many are deep within the housing of the wrench or power tong and require a disassembly of the wrench and order that they be adjusted and/or replaced. Further, many of the above devices have no adjustability with respect to the brake shoe and brake drum portions, thus having no way to adjust the torque applied by the wrench or to compensate for wear or either the brake or drum structure. At least one device above (U.S. Pat. No. 3,516,308) does provide an adjuster screw, which can be adjusted to get more or less braking force to the tong assembly. However, in that patent to J. E. Ham and Merrill Willsey, the adjustable screw is unbalanced and difficult to adjust. Further, the entire assembly is not freely available for inspection and/or replacement.
Most prior art devices are difficult and/or impossible to replace in the field should the need arise. Further, they are plagued by the problem of adjustability of the frictional contact of the drum and shoe during operation of the wrench. Further, they often require extensive use of extra tools to precisely vary the torque provided by the wrench through the braking assembly if such adjustability is available at all.
Those devices which have braking members which are within the housing of the wrench usually require shop maintenance removed from the site of the use of the tong in order to properly repair, replace, and/or adjust the braking apparatus.
3. General Description of the Present Invention
The present invention provides an improved power tong brake apparatus which utilizes a preferably integral brake drum body provided with an outer bearing surface. The brake drum body is affixed to the power tong at the jaw carrier portion thereof with the bearing surface portion of the brake drum body projecting externally to the outside of the power tong housing when affixed thereto during operation.
An adjustable brake shoe adapted for frictional engagement with the brake drum is provided and also externally mounted on the outer frame portion of the power tong with the shoe being movably adjustable on the power tong frame with respect to the drum.
In the preferred embodiment, the brake drum is an integral single body having a downwardly depending cylindrical drum portion provided with an outer curved drum bearing surface. The drum surface is entirely external to the power tong itself and thus easily accessible by a driller, repairman, or other technical person when adjustment is required. The brake shoe can be for example, semi-circular in structure and attaches to the external portion of the power tong frame and registers with and contacts frictionally the brake drum at its outer circular bearing surface. The brake shoe is provided with an external adjustment which allows it to be quickly and easily moved and adjusted with respect to the brake drum surface minimizing down time, minimizing repair time, and maximizing production of the oil well or other installation to which the entire power tong apparatus is assigned.
Therefore it is an object of the present invention to provide an improved power tong brake apparatus which is generally external to the power tong allowing easy access thereto.
It is another object of the present invention to provide an adjustable power tong brake apparatus which is generally externally adjustable and easily adjustable in the field where the power tong is being utilized.
It is further object of the present invention to provide a power tong brake apparatus which is simple in structure and simple to manufacture, and requiring little maintenance.
It is another object of the present invention to provide a power tong brake apparatus providing a semi-circular brake shoe, which is externally mounted to the power tong and is externally adjustable on the power tong with respect to the brake drum.
A feature of the present invention is that it can be externally adjusted with conventional tools in the field at the site of the oil well, gas well, or other installation or job to which the power tong is being used.
Another feature of the present invention is that it provides a power tong brake apparatus which includes a brake drum and brake shoe, which are mutually separate parts that can be individually changed without the changing of the other part associated therewith.